Medieval Temples and Arms — Sohei Swords and Their Influence on Japanese Sword Development

Militarization of Temples in Medieval Japan

From the Heian period through the Muromachi period, many Buddhist temples in Japan organized themselves as independent military forces. This phenomenon developed within a historical context unique to Japan, differing from the militarization seen in Christian monasteries in Western Europe.

Particularly over approximately 400 years from the 12th through 16th centuries, armed practitioners known as sohei (僧兵) wielded significant influence over Japan's politics and military affairs. Their existence played a role in the history of Japanese sword development that cannot be ignored.

The Formation and Development of Sohei

Militarization as a Means of Self-Defense

In the mid-Heian period (10th-11th centuries), major temples in Kyoto—including Enryakuji, Todaiji, and various temples in Nara—embarked on militarization primarily out of necessity for self-defense.

As attacks on temple lands by regional estate lords and bands of thieves increased, temples found themselves compelled to develop defensive capabilities. Additionally, territorial disputes between temples were increasingly settled by force.

Under these circumstances, the disciples of temples began to receive military training alongside their religious practice, which eventually led to the establishment of the sohei class.

Organization and Consolidation of Sohei Power

From the 12th through 13th centuries, sohei organizations became increasingly systematic. The sohei of Enryakuji developed into armed groups numbering in the hundreds to thousands, exerting direct influence over Kyoto's politics and military affairs.

At one point, their power became so great that the imperial court and shogunate were compelled to change their policies in response to sohei demands. Sohei leaders cooperated with temple elders (shutu) and conducted increasingly organized military operations.

Sohei and the Technical Development of Japanese Swords

Actual Combat and Improvements in Sword Performance

The swords used by sohei were not mere ceremonial implements, but practical weapons repeatedly used in actual combat. Consequently, sword makers found themselves forced to forge blades with greater strength and superior durability in response to sohei demands.

In particular, the development of large naginata and tachi designed for simultaneous combat against multiple opponents was a challenge that drove swordsmiths of the 12th-13th centuries.

Technical Exchange with Kamakura Warriors

After the Genpei War at the end of the 12th century and the establishment of Kamakura shogunate rule, military exchange between sohei and Kamakura warriors became active. Sword manufacturing technology developed while experiencing mutual influence from both sides.

Many of the innovative forging techniques adopted by the Soshu school (a group of swordsmiths in Sagami Province) were developed through contact with Kamakura warriors, while sohei from Enryakuji and Todaiji also benefited from these new techniques.

Temple Military Power and Political Influence

Political Pressure Exerted by Sohei

From the 12th through 14th centuries, incidents in which sohei from Enryakuji and Eizan marched into Kyoto and made political demands reportedly occurred dozens of times. Such use of force sometimes even influenced imperial decisions.

Particularly during the Nanboku-cho period (14th century), sohei from various temples divided into different camps and participated in military operations. During this period, sohei increasingly took on the character of purely armed organizations.

Expansion of Regional Control

Temple power from the Heian through Muromachi periods did not remain limited to the Kyoto area. Major temples such as Enryakuji and Negoro-ji maintained branch temples throughout the country, where they also organized sohei forces.

These regional temple sohei sometimes clashed with local lords and sometimes cooperated with them, exerting significant influence on local politics and military affairs.

Naginata and the Weaponry of Medieval Sohei

Development of the Naginata

One weapon in which sohei excelled was the naginata. This weapon, with its curved blade at the end of a long shaft, was easy to handle both on horseback and on the ground.

The blade portion of the naginata ranged in length from a short sword to that of a tachi, and by attaching this to a long shaft, slashing attacks from a distance became possible. This weapon proved particularly effective in group combat among sohei.

Tactics of Group Combat

Sohei developed unique tactics using the naginata in group combat. The following types of organized combat formations took shape:

• A formation called "kurumakakari" in which multiple sohei lined up to face and counter attackers
• Wave-like attacks with continuous group slashing

This tradition of group combat later exerted great influence on group tactics during the Muromachi period.

Religious Background and the Contradiction with Military Force

The Conflict Between Buddhist Peaceful Ideology and Militarization

The existence of sohei fundamentally contradicted the core Buddhist doctrine of "killing no living thing" (fushsho). In response to this contradiction, sohei attempted various theoretical justifications, for example:

• The argument that their use of force was "a necessary action taken to protect temple property and believers"
• The interpretation that defeating an enemy was "part of one's practice"

Such logic later influenced the formation of the warrior's honorable view of life and death.

The Path to Decline

In the 16th century, with Oda Nobunaga's suppression of Buddhist forces, sohei power declined significantly. In particular, the burning of the Hiei Mountain Enryakuji temple (1571) became a symbolic event marking the decline of sohei military power. Thereafter, with the unification and establishment of peace during the Edo period, sohei gradually disappeared from the historical stage.

Conclusion

The militarization of temples and the activities of sohei in medieval Japan were not a temporary abnormality in history, but rather phenomena that reflected the very structure of medieval society. The practical combat experience of sohei and the technological innovations of swordsmiths responding to their demands were one of the driving forces that led to Japanese swords gaining their high reputation.

Additionally, the tradition of military force by sohei and the accompanying logic of religious justification exercised deep influence on the formation of bushido ideology—including the samurai's honorable view of life and death and the culture of seppuku—which became unique to Japan.